The present invention relates to an antenna assembly suitable for wireless transmission of analog and/or digital data, and more particularly to a multiple band antenna assembly for use with wireless communication devices.
Wireless communication devices such as cell phones, global positioning system transceivers and hand held computers are becoming an integral part of society. Aside from obvious advantages of cordless operation, one reason that such devices have become so popular, of late, is due to the trend toward smaller and more compact overall size of such devices. Where once a typical wireless communication device (WCD) evoked images of a large, heavy, bulky device with a whip antenna, today""s typical wireless communication device is small, lightweight, and easily transported. As the wireless communication devices have become smaller, antennas have evolved both in terms of location and structure. There is an increasing trend away from the external antenna not only because it is subject to breakage, but also because it operates in an omni-directional manner. Antennas which generally do not have the drawbacks to the aforementioned external antenna include internal antenna assemblies. These antennas typically may include a resonator element which is electrically connected to a comparatively larger planar conductor which functions as the second half of an asymmetric dipole. The planar conductor (which may be a ground plane of a wireless device) is usually rectangle-shaped having a longitudinal dimension which establishes a principal polarization. The planar conductor may be provided by a conductive element (such as the ground plane) associated with the printed wiring board of the wireless communication device and fabricated along with the printed wiring board using conventional techniques and technologies.
There also continues to exist in the art a need for an antenna assembly which does not have protruding elements which may injure human users and/or which are inherently susceptible to damage including breakage which might render such wireless communication devices inoperable. In addition, there exists in the art a need for an antenna which directs electromagnetic waves away from a human user of wireless communication devices and has a reduced specific absorption rate (SAR) function. In keeping with the continuing trend toward smaller, efficient, yet more compact wireless communication devices, there exists in the art a need for an operable antenna assembly which is not constrained to predetermined dimensions and whose component and assembly size may be reduced, adjusted and/or selected to provide optimal operation without regard to heretofore fixed design constraints. The inventor of the present invention also recognizes the general need in the art of wireless communication device design and implementation for a suitable antenna assembly in which components are modular and/or readily interchangeable. And, there is a need for an antenna assembly which is compact, lightweight and which may be incorporated into a variety of wireless communication devices.
The present invention involves and encompasses an antenna assembly having an inventive ground plane design susceptible of a variety of implementations in the field of compact wireless communication device (WCD) component design. The present invention is directed to a family of antenna assemblies that effectively function within the desired bandwidth and gain of known, prior art antenna assemblies having a larger, single surface ground plane. The modified ground plane includes a first and second conductive portion adjacent to each other in a non-conducting relation yet operatively electrically coupled to each other by at least one electrically conducting element. The resulting assembled conductor has an effective electrical path composed of the longitudinal dimension of the first and the second conductive portion but which has electrical operational characteristics of a singular ground plane conductor. The effective electrical path includes the axial length of the electrically conducting element that electrically couples the first and second conductive portion. This feature facilitates a variety of desirable operating characteristics while allowing mass production of more compact WCD designs.
In the preferred embodiment, at least a first and a second conductive portion formed on a generally rectangular common base member has confronting edges separated from each other. In one embodiment said separation is on the order of between approximately one and six millimeters (xcx9c1.0 mm to 6.0 mm) with a preferred embodiment having a value of slightly less than about three millimeters (2.9 mm). The first and second conductive portion are electrically coupled by at least one conducing element (or connecting link) operatively connecting the first and second conductive portion together. In a preferred embodiment, the electrically conducting member commonly comprises a copper wire having an outside diameter of around 0.80 mm and formed into the shape of the letter xe2x80x9cc.xe2x80x9d It should be noted that the particular shape of the conducting element depends somewhat upon the length of the conducting element and may take other forms, including an xe2x80x9cS-shape,xe2x80x9d a xe2x80x9cZ-shape,xe2x80x9d or other varieties of shapes. In this regard, one may also utilize other types of inductor links and/or capacitive elements and multiple links may be used whether or not they are identical to other of said conducting elements used in a given ground plane constructed according to the present invention. Of course, in more complex configurations, the shape of the electrically conducting, connecting link member(s) may need to be shielded or insulated so that the desired electrical pathway is not compromised. Indeed, as appreciated by those of skill in the art, and as described and taught herein, the axial length of the electrically connecting member(s) supplies a significant portion of the advantages of the present invention.
The conducting element is preferably disposed upon a side of the base member which may be a printed wiring board of the device. However, in another embodiment of the present invention, the first and second conductive portion may be disposed on opposing sides of the base member to facilitate compact construction. In addition, more than two conductive portions may be electrically coupled together in accordance with the present invention to match the impedance of the antenna and produce the frequency band-width or pattern beam-width required for quality signal characteristics.
In one form of the present invention, a substantially planar ground plane having said conductive portion(s) disposed on at least one surface thereof typically includes a resonator (which may be modular) and an optional feed line which may be operatively connected to various devices through an appropriately sized surface mount adaptor. Although the ground plane may be disposed upon a flexible, or deformable, base member other embodiments may include a non-planar assembly of printed wiring boards. In any event, the resultant split ground plane antenna assembly of the present invention is not only compact, but exhibits a desirable low specific absorption rate (SAR) function. The split ground plane has an effective electrical length (in a longitudinal dimension) substantially comprised of the length of the two separated conductive elements in addition to the effective length of the connecting element. Thus, by forming an electrical coupling between the two conductive planes an effectively increased overall ground plane is enabled within a smaller, more compact overall physical envelope.
Split ground plane antennas as disclosed, enabled, and illustrated herein function i properly using an effective conductive plane with operational characteristics typical of much larger antenna in terms of performance and overall footprint requirements. Additionally, antenna designed according to the present invention may be configured to operate in either a single band or a multiple band mode depending on the resonator element(s) associated with the antenna assembly. Finally, antenna constructed according to the present invention can comprise any number of antenna components or resonator types as would be obvious to those of skill in the art to which the present invention is directed. Indeed, those of skill in the art shall immediately recognize that a variety of types of split gap ground plane antennas result from application of the teaching herein. For example, a plurality of gap features between and among said ground plane (and related electrically conducting connector members) may be implemented including a wide variety in the number of gaps, size of the spacing of the gaps (including parallel and non-parallel spacing comprising said gap features), dimensions of the conducting connector members, and locations of said gaps are all susceptible to application of the teaching herein. Additional components such as but not limited to capacitive and/or inductive assemblies may well be employed within a connecting link to produce useful iterations of the present invention as is understood by those of skill in the art to which the invention is directed.
It is an object of the present invention to provide an antenna assembly which may be incorporated into a wireless communication device.
Another object of the present invention is to reduce the dependence of the dimensions of a ground plane on a particular wavelength or fractional portion thereof.
Another object of the present invention is to facilitate more overall compact construction in a wireless communication device.
Yet another object of the present invention is to minimize the need for an antenna matching network.
A feature of the present invention is that the combined ground plane comprises two conductive elements which are operatively connected to each other.
Another feature of the present invention is that the conductive ground plane may be operatively connected to a variety of resonator elements.
Another feature of the present invention is that fabrication may be accomplished through existing technologies and mass production techniques.
An advantage of the present invention is that the antenna assembly has a low profile which enables it to be used in small articles such as wireless communication devices.
Another advantage of the present invention is that the split conductive plane is able to operate as if it in fact comprised a traditional larger, singular conductive plane and that enables multi-band and single band frequency sensitivity and operation.
These and other objects, features and advantages will become apparent in light of the following detailed description of the preferred embodiments in connection with the drawings. Of course, as appreciated by those of skill in the art to which the present invention is directed the following detailed description and drawings are intended as illustrative and not limiting as to the scope of the present invention claimed herein, and that many variations and subtle changes may be made in designing antenna assemblies according to the teaching herein without departing from the spirit and scope of the present invention as defined in the appended claims hereto.